Well drilling is a complex science and if done incorrectly can result in disaster. As oil exploration reaches deeper levels, as shown in the recent Deepwater Horizon disaster, the depth of the well creates extreme pressures causing known drilling methods to fail. (For example, using a cement plug or the ability to sheath a pipe with cement). When these known methods fail, the well itself may not be in the proper condition to install either a conventional cap or blowout preventer.
In the Deepwater Horizon disaster, a blowout preventer, a set of valves which sits on the sea floor at the top of the MC252 well, which was drilled by the ill-fated rig, Deepwater Horizon, was riddled with leaks. Originally the preventer was linked to the Deepwater Horizon by a mile long vertical pipe called a riser, through which oil would flow. When the Deepwater Horizon sank, this riser collapsed and folded in on itself, but did not sheer off from the blowout preventer. As a result, much of the leaking oil would flow out of the blowout preventer and into the twisted riser, from which it emerges about 300 meters (1,000 feet) away.
To effect a stoppage of the oil emanating from the blowout preventer, a cofferdam was lowered over the riser extending from the top of the blowout preventer to direct the leaking oil flow straight up to the surface through a new riser lowered from a drillship. Unfortunately, simply trapping the oil coming out of the end of the riser failed because of icy hydrates formed in the cofferdam by the gas coming out of the well. No means exists in the art to exploit the riser itself as a part of a physical fixation of a cofferdam to contain and redirect oil through a riser system for collection at the surface.